1. Field of the Invention
This invention relates to the use of a single "hold-out" coating layer applied by the paper machine on the press-applied. barrier side of a paperboard substrate. Such structures of this type, generally, allow paper machines with only one coater on the barrier side to apply a sufficient coating for the desired hold-out.
2. Description of the Related Art
It is known, in paperboard carton production, to produce a carton with a press-applied coating on the nonclay-coated side. Due to the lack of hold-out, severe pin-holing of the press-applied coating can result. On a clay-coated side, a nearly pin-hole free, press-applied film can be achieved. However, during folding and scoring operations, pin holes may develop in corners and seams and can result in the food product attacking the paperboard layer resulting in catastrophic failure. Also, if a clay-coated surface is required beneath the press-applied film, this may require exterior printing on a non-clay coated side if C1S (coated one side) paperboard is used. This may dramatically reduce the print quality of the package. Consequently, a more advantageous coating, then, would be presented if the hold-out could be improved.
It is also known, in the papermaking industry, to make use of a colloidal copolymer such as styrene-butadiene resin (SBR). The SBR is specifically used as a coating binder in papermaking. Advantages of the SBR are a better gloss, inking, resistance to moisture and a more relaxed and flexible coating. Exemplary of such prior art are U.S. Pat. No. 2,537,114 ('114) to A. E. Young et al., entitled "Pigment Coated Paper" and U.S. Pat. No. 2,685,571 ('571) to J. C. Stinchfield, entitled "Mineral-Coated Paper and Composition Therefor". While the '114 and '571 patents employ the use of a SBR, the SBR is not used to increase the desired hold-out. Consequently, a still further advantageous coating, then, would be presented if the SBR could be used in order to increase the hold-out.
It is apparent from the above that there exists a need in the art for a press-applied polymer layer which can be applied to paperboard cartons and packages, but which at the same time can be used to enhance press-applied barrier hold-out of the board. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.